1. Field of the Invention
The present invention relates to large cooling fans and, in particular, concerns a hub assembly for large cooling fans.
2. Description of the Related Art
Cooling fans are often used in industrial applications. In some industrial spaces, the ability to use air conditioning is reduced due to ventilation concerns. For example, in buildings where welding or other oxidizing processes are performed, it may be necessary to have the building open to the outside air for ventilation purposes.
To address these concerns, large industrial fans have been developed. One such example of a large industrial fan is disclosed in U.S. Pat. No. 6,244,821 ('821) to Walter Boyd et al. The fan disclosed in the '821 patent is a large fan having air foil shaped blades that can exceed 8 feet in length. It is particularly adapted to be mounted on the ceiling of an industrial space to provide a cooling airflow for a large volume interior space. The fan in the '821 patent can also be adapted for wall mounting as well.
One issue that occurs with fans with very large blades is that the mounting between the fan blades and an associated hub can be complicated. As the size and weight of the blades of the fan are large, the resultant forces on the hub can be significant. It is desirable that the hub and the interconnection between the blades and the hub be sufficiently strong so as to retain the blades on the hub during normal operation as blades falling off the fan can represent a significant hazard.
This problem is often exacerbated by the environment in which the fans are used. Typically, these fans are used inside buildings that are exposed to the outside air. Wind gusts and the like can exert significant forces on the blades of the fan causing the blades to be more prone to break, often at the point of attachment to the hub.
In the '821 patent, the hub is formed of a casted metal component that is bolted to the fan blade at a plurality of different locations. The casted hub is formed of a single integrated unit which improves the overall strength of the hub. However, having a casted hub represents a significant increase in the overall cost of the fan assembly. Moreover, when a hub blade does break, the entire hub assembly has to be disassembled and replaced and then reassembled which increases the cost and time of repair.
Further, with existing hubs, the fan blades are bolted at one or two locations to the hub blades. Bolting the fan blades to the hub at discrete locations results in the forces between the hub and the fan blades being concentrated at those discrete locations. This can represent a potential point of failure of the blades with respect to the hub assembly.
From the foregoing, there is a need for an improved fan assembly that is less expensive to manufacture, easier to repair and provides a better system for transmitting forces between the hub assembly and the fan blade.